Method and apparatus for correcting motor imbalance

ABSTRACT

A blower assembly includes a motor including a shaft extending therefrom and a blower wheel including a hub. The blower wheel is attached to the motor shaft. A first slot extends through the hub and a second slot extends through the hub. The first slot is angularly displaced around the hub about 180 ° from the second slot.

BACKGROUND OF INVENTION

[0001] This invention relates generally to motor assemblies and more particularly to blower motor assemblies.

[0002] Conventional blower assemblies include a motor having a shaft with a single flat and a blower wheel hub attached to the shaft with a set screw tightened against the flat to secure the hub to the shaft. Alternatively, other known blower assemblies include a shaft having two flats and two set screws angularly spaced 90° from one another. Typically, blower motor wheels are balanced prior to assembly. However, imbalance of the rotor and shaft extension runout will either add to, or subtract from, any remaining wheel imbalance. Because the effects of these imbalances are phased, excessive vibration due to rotating imbalance can occur even with motor, blower wheel, and shaft eccentricities within component process capability.

[0003] One method of alleviating excessive imbalance is to replace the blower wheel or motor. In addition, trim balancing the blower assembly or balancing the rotors prior to assembly may also effectively reduce imbalance. However, such methods add to the cost of the blower assembly.

SUMMARY OF INVENTION

[0004] In one aspect, a blower wheel hub is provided which comprises a body, a first threaded slot extending through the body, and a second threaded slot extending through the body. The first slot is angularly displaced around said body about 180° from the second slot.

[0005] In another aspect, a blower assembly is provided which comprises a motor comprising a shaft extending therefrom. The blower assembly also comprises a blower wheel comprising a hub. The blower wheel is attached to the motor shaft. A first slot extends through the hub and a second slot extends through the hub. The first slot is angularly displaced around the hub about 180° from the second slot.

[0006] In another aspect, a furnace system is provided which comprises a furnace and a blower assembly positioned within the furnace. The blower assembly comprises a motor comprising a shaft extending therefrom and a blower wheel comprising a hub. The blower wheel is attached to the motor shaft. A pair of slots extend through the hub and are angularly displaced around the hub about 180° apart.

[0007] In a further aspect, a method is provided for correcting imbalance in a blower assembly including a motor and a blower wheel. The motor includes a shaft extending therefrom and is configured to engage the blower wheel. The method comprises disengaging the blower wheel from the shaft, rotating the blower wheel 180°, and engaging the blower wheel with the shaft such that rotation of the shaft causes rotation of the blower wheel.

BRIEF DESCRIPTION OF DRAWINGS

[0008]FIG. 1 is a schematic diagram of a furnace system.

[0009]FIG. 2 is a schematic diagram of a known blower motor assembly.

[0010]FIG. 3 is a schematic diagram of a blower motor assembly in accordance with one embodiment of the present invention.

DETAILED DESCRIPTION

[0011]FIG. 1 is a schematic diagram of a furnace system 30, such as a Model RGRA-10EZAJS furnace system commercially available from Rheem Manufacturing Company, Fort Smith, Ark., configured to heat a space 32. In an alternative embodiment, the system is an air circulating system such as a heating, ventilation, and air conditioning (HVAC) system configured to heat or cool a space.

[0012] Included in system 30 are a thermostat 34, a heating source 40, a blower motor assembly 42 and an air flow path 44. Blower assembly 42 is positioned within furnace system 30 and includes a motor (not shown) such as a GE ECM Programmable motor, model number 5SME39SL0324 commercially available from the General Electric Company, Schenectady N.Y., and includes a motor controller (not shown) configured with a microprocessor and a memory containing a control program. Motor assembly 42 also includes a blower wheel (not shown), such as a 03-66021 12-11 0.50 CLW CV commercially available from Morrison Products Inc., Cleveland, Ohio, attached to the motor. The motor controller is configured to be electrically connected to thermostat 34 which controls the turning off and on of heating source 40. The selection of heating or fan only for heating source 40 using thermostat 34, implies a selection of fan speed for the blower motor. Higher fan speeds are typically used for heating while a lower fan speed is used for fan only to circulate air throughout system 30.

[0013] Thermostat 34, in one embodiment, is configured as a system controller. In such an embodiment, the motor controller is electrically connected to thermostat 34 and is configured to receive information from thermostat 34 regarding operation and performance of system 30, as thermostat 34 controls operation of heating source 40 and the blower motor. The motor controller can be configured for the monitoring of air flow, static air pressure, temperature or any other parameter relative to heating and air flow.

[0014]FIG. 2 is a schematic diagram of a known blower motor assembly 50 that can be utilized in a furnace system, such as system 30 shown in FIG. 1. Blower motor assembly 50 including a motor 52 having a shaft 54. A blower wheel (not shown) includes a hub 56 and is connected to motor shaft 54 with hub 56. In one embodiment, shaft 54 includes a flat 58 extending from an end thereof. Hub 56 includes a threaded slot 60 and a set screw 62 threadably engaged with slot 60.

[0015] Screw 62 secures hub 56 to shaft 54 by contacting flat 58.

[0016]FIG. 3 is a schematic diagram of a blower motor assembly 70 in accordance with one embodiment of the present invention. Motor assembly 70 includes a motor 72 having a shaft 74 extending therefrom. Motor assembly also includes a blower wheel (not shown) including a hub 76 having a body 78. The blower wheel is attached to motor shaft 74 with hub 76. Shaft 74 includes a flat 80 extending from an end thereof. In one embodiment, hub 76 is substantially tubular and encircles a portion of shaft 74.

[0017] Hub 76 includes a first threaded slot 82 extending through body 78 and a second threaded slot 84 extending through body 78. In one embodiment, first slot 82 is angularly displaced around body 78 about 180° from second slot 84. Hub 76 also includes a set screw 86 threadably engaged with first slot 82. Screw 86 secures hub 76 to shaft 74 by contacting flat 80 and being tightened against flat 80 such that hub 76 rotates with shaft 74. In one embodiment, first slot 82 and second slot 84 are substantially the same size and second slot 84 is configured to threadably receive screw 86.

[0018] If after assembly of the blower motor assembly 50, an imbalance is detected, set screw 86 can be removed from hub 76 and hub 76 can be re-positioned on shaft 74 to improve the balance of assembly 50 without removing hub 76 from shaft 74. A method for correcting imbalance in blower assembly 50 includes disengaging blower wheel hub 76 from shaft 74 by threadably removing set screw 86 from first slot 82 and removing blower wheel hub 76 from shaft 74. Blower wheel hub 76 is rotated approximately 180° with respect to shaft 84 and is re-engaged with shaft 74 causing rotation of hub 76 with shaft 74. Specifically, hub 76 is repositioned on shaft 74 such that second slot 84 is aligned with shaft flat 80 and set screw 86 threadably engages second slot 84 such that screw 86 contacts flat 80 thereby securing hub 76 to motor shaft 74. This repositioning of hub 76 changes the phase of the imbalance and alleviates at least some of the imbalance.

[0019] Although hub 76 has been described with two threaded slots spaced approximately 180° apart, it should be understood that three or more slots could be used to provide more position variations of hub 76 with respect to shaft 74.

[0020] While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims. 

1. A blower wheel hub for connecting to a motor shaft, said hub comprising: a body; and a first threaded slot extending through said body and a second threaded slot extending through said body, said first slot angularly displaced around said body about 180° from said second slot.
 2. A blower wheel hub in accordance with claim 1 wherein said first and second slots are configured to threadably receive a set screw.
 3. A blower wheel hub in accordance with claim 1 wherein said slots are substantially the same size.
 4. A blower assembly comprising: a motor comprising a shaft extending therefrom; a blower wheel comprising a hub, said blower wheel attached to said motor shaft; and a first slot extending through said hub and a second slot extending through said hub, said first slot angularly displaced around said hub about 180° from said second slot.
 5. A blower assembly in accordance with claim 4 wherein said shaft comprises a flat.
 6. A blower assembly in accordance with claim 4 wherein said first and second slots are configured to threadably receive a set screw.
 7. A blower assembly in accordance with claim 5 wherein said hub is aligned on said shaft such that a set screw positioned within said first slot contacts said flat and secures said hub to said shaft.
 8. A blower assembly in accordance with claim 5 wherein said hub is aligned on said shaft such that a set screw positioned within said second slot contacts said flat and secures said hub to said shaft.
 9. A residential furnace system comprising: a furnace; a blower assembly positioned within said furnace, said blower assembly comprising: a motor comprising a shaft extending therefrom; a blower wheel comprising a hub, said blower wheel attached to said motor shaft; a pair of slots extending through said hub and angularly displaced around said hub about 180° apart.
 10. A furnace system in accordance with claim 9 wherein said shaft comprises a flat.
 11. A furnace system in accordance with claim 9 wherein said pair of slots comprises a first slot and a second slot, each said slot configured to threadably receive a set screw.
 12. A furnace system in accordance with claim 11 wherein said hub is aligned on said shaft such that a set screw positioned within said first slot contacts said flat and secures said hub to said shaft.
 13. A furnace system in accordance with claim 11 wherein said hub is aligned on said shaft such that a set screw positioned within said second slot contacts said flat and secures said hub to said shaft.
 14. A furnace system in accordance with claim 11 wherein said first slot and said second slot are substantially the same size.
 15. A method for correcting imbalance in a blower assembly including a motor and a blower wheel, the motor including a shaft extending therefrom and configured to engage the blower wheel, said method comprising: disengaging the blower wheel from the shaft; rotating the blower wheel 180°; and engaging the blower wheel with the shaft such that rotation of the shaft causes rotation of the blower wheel.
 16. A method in accordance with claim 15 wherein the blower assembly further includes a set screw and the blower wheel includes a blower wheel hub, the blower wheel hub including first and second slots angularly spaced about 180° from each other, the motor shaft including a flat, the blower wheel first and second slots configured to threadably receive the set screw, said step of disengaging the blower wheel from the motor shaft comprises threadably removing the set screw from the first slot.
 17. A method in accordance with claim 15 wherein the blower assembly further includes a set screw and the blower wheel includes a blower wheel hub, the blower wheel hub including first and second slots angularly spaced about 180° from each other, the motor shaft including a flat, the blower wheel first and second slots configured to threadably receive the set screw, said step of engaging the blower wheel with the motor shaft comprises: positioning the blower wheel on the shaft such that the second slot is aligned with the shaft flat; and threadably engaging the set screw with the second slot such that the set screw contacts the motor shaft flat thereby securing the blower wheel to the motor shaft. 